This disclosure relates to a cutting tool comprising a holder and a cutting insert arranged exchangeably in the holder. The disclosure further relates to the cutting insert for such a cutting tool and to the holder for this cutting tool.
Cutting tools of this type are generally used in metal-machining applications, in particular in milling or turning applications. Cutting tools according to the present disclosure are used, in particular, for plunge-cut turning or longitudinal turning. In order to ensure optimal machining properties, a, from a mechanical aspect, stable insert seat, i.e. a mechanically stable reception of the cutting insert within the tool holder, is of huge importance. To this end, the employed cutting inserts are clamped in place or held clamped in a receptacle, provided in the tool holder, between two clamping jaws. A further important aspect which it is important to ensure is fast and simple exchangeability of the cutting insert, since this has to be frequently exchanged due to wear.
EP 0 312 223 A1 shows a tool comprising a substantially prismatically shaped cutting insert, which has a concave top side and a convex bottom side. The cutting insert is here disposed between a rigid lower clamping jaw and an elastically expandable upper clamping jaw in the holder. The clamping force for clamping the cutting insert between these two clamping jaws is generated by a clamping screw. In order to be able to release the cutting insert from the holder in the event of an exchange, the clamping screw must therefore be manually loosened and then manually retightened as soon as a new cutting insert is inserted in the holder. This is not only laborious, but also time-consuming. Particularly in cramped installation situations, which frequently arise in machine tools, this is often possible only with great difficulty, sometimes even not at all possible, without removing the holder itself from its clamping.
EP 1 205 273 A1 shows a further cutting tool, which consists of a disk-shaped or blade-shaped basic element having at least one recess for the reception of a cutting insert. The cutting insert is exchangeably clamped in place by an elastically expandable clamping arm, which forms the upper locating face of the recess. The cutting insert and the recess are constructed in positive locking design on their mutual locating faces. As a result, a so-called “self-clamping principle” is realized. A clamping screw as is necessary according to EP 0 312 223 A1 can thereby be dispensed with. In order to be able to exchange the cutting insert, the upper clamping arm must here be manually expanded. It has been shown that in such a case an enduringly stable insert seat cannot always be guaranteed. A frequent expansion of the upper clamping arm can occasionally lead to cases of material fatigue, whereby the clamping force between holder and cutting insert would not be permanently guaranteed.
Due to the essential elastic properties of the upper clamping jaw, an expandable slot which opens out into the holder-side end of the cutting insert receptacle is respectively necessary both in the tool known from EP 0 312 223 A1 and in the tool known from EP 1 205 273 A1. Without these expandable slots, the upper clamping jaws would respectively be rigidly configured, so that they could no longer be expanded, or only with huge force expenditure. Although such expansion slots should not fundamentally be regarded as disadvantageous, the installation space which has to be provided on the holder is nevertheless thereby increased, with the result that compact tools or compact holders can be guaranteed in such an embodiment only with great difficulty. Moreover, the provision of such an expansion slot demands a further machining step in the manufacture of such a holder. The production of such expansion slots can occasionally be relatively complex. Moreover, care must here be taken to ensure that the overall stability of the clamping head is maintained despite the expansion slot.
It should further be pointed out that, in both above-stated tools known from the prior art, the cutting insert bears respectively with its holder-side face against the tool holder. To this end, in both tools locating faces are provided in the floor of the cutting insert receptacle. In the tool which is known from EP 0 312 223 A1, an extra limit stop element is even arranged for this purpose in the floor of the cutting insert receptacle. In both cases, as a result of such a limit stop or as a result of such a contact, a sufficiently exact tip height can be realized only by means of very narrow production tolerances.